A rainstick is a long, hollow tube partially filled with small pebbles or beans that has small pins or thorns arranged helically on its inside surface. When the stick is upended, the pebbles fall to the other end of the tube, making a sound reminiscent of rain falling. It is designated 112.1+133.1 in the Hornbostel–Sachs classification system.

The rainstick is believed to have been invented by the Aztecs and was played in the belief it could bring about rainstorms. Rainsticks are usually made from any of several species of cactus. The cacti, which are hollow, are dried in the sun. The spines are removed, then driven into the cactus like nails. Pebbles or other small objects are placed inside the rainstick, and the ends are sealed. A sound like falling water is made when the rainstick has its direction changed to a vertical position.

Although it was thought to have been invented in Mexico, many similar instrument can also be found in Southeast Asia and Africa which is often made in bamboo rather than dried cactus.

Rainsticks may also be made with other common materials like paper towel rolls instead of cactus, and nails or toothpicks instead of thorns and are often sold to tourists visiting parts of Latin America, including the Southern United States.